1. Field of the Invention
The present invention relates to method for forging a metallic blank in order to form a cup-shaped product having a flange at an outer surface thereof. The product made by the present forging method is useful for use as a pulley, for example.
2. Description of the Prior Art
Conventionally, a cup-shaped product having a flange at an outer surface thereof is formed by forging from a metallic blank. However, according to the conventional forging method, the flange portion must be forged as a different step from that of the cup portion. As described in Japanese patent publication No. 55-49876, a cup portion is forged first, then a flange portion is formed by another forging step.
Such conventional steps are described with reference to FIGS. 13-15.
The metallic blank 100 having such shape as shown in FIG. 13 is forged in order to be a cup-shaped metallic member as shown in FIG. 14. Then a thick portion 105 of the metallic member 104 shown in FIG. 14 is forged again in order to be the shape shown in FIG. 15.
As described above, the conventional forging method has to employ a plurality of forging steps, so that the conventional method has a problem of expending much cost and much working time.